1. Field
This disclosure relates generally to semiconductor devices, and more specifically, to semiconductor devices with embedded stressors.
2. Related Art
Embedded stressors have been found to be effective in increasing transistor performance by increasing carrier mobility. The typical process includes forming recesses in the source/drain regions and then filling the recesses with a semiconductor material that acts as a stressor to provide stress to the channel while also being effective as a source/drain. For the channel being silicon, the use of silicon germanium stressors has been found to be effective for the P channel transistors and silicon carbon has been found to be effective for N channel transistors. To increase stress and thereby increase transistor performance, the stressors are desirable adjacent to the channel. Thus a benefit of the stressors being immediately adjacent to the channel is maximizing the stress to the channel. The cost of this benefit can be increased leakage due to loss of short channel control if the stressors continue straight down from the lateral edge of the channel. Thus, a benefit is seen in attempting to provide a stressor that is shallow in the area immediately adjacent to the channel to and is deep in the area where the source/drain contact is formed. This then brings the stressor adjacent to the channel to increase transistor performance while not degrading current leakage. This can be achievable but has been found to add processing complexity.
Accordingly there is a need to achieve the benefits of embedded stressors while avoiding or reducing the problems associated with making them.